Field Of The Invention
The invention relates to a nuclear power installation with a high-temperature pebble bed reactor, whose core consists of a pile of spherical fuel elements which is surrounded on all sides by a reflector. A cooling gas flows through the core from the bottom to top. The nuclear power plant has a heat utilization system which is arranged above the high-temperature pebble bed reactor and located, along with said reactor, in a multi-component, cylindrical, steel pressure vessel. The heat utilization system also has cooling gas flowing through it from bottom to top. The nuclear power plant also has at least two circulating blowers adjusted to the direction of flow of the heat utilization system, and two shut-down arrangements comprising absorber elements of different types.
A high-temperature reactor with spherical fuel elements (AVR installation) is known in which the heat utilization system consists of a steam generator arranged above the reactor. The blowers for circulating the cooling gas, flowing from bottom to top through the reactor core, are located under the reactor core in this nuclear reactor. In case the blowers fail, the residual heat is transferred by natural convection to both the heat generator and the constructions surrounding the reactor core. The latter comprises, in addition to a graphite reflector jacket, a carbon brick jacket. In order to safely contain the fission products released, the nuclear reactor and the steam generator are surrounded by a double steel pressure vessel. For the shut-down of the nuclear reactor, absorber rods are provided, which may be inserted from the top into graphite columns located in the reactor core. There are no additional shut-down arrangements.
The state of the art further includes a nuclear reactor installation with a high-temperature pebble bed reactor and a plurality of steam generators housed, together with the reactor, in a cylindrical steel pressure vessel (German Offenlegungsschriften Nos. 32 12 264 and 32 12 266). Cooling gas flows from bottom to top through the reactor core. The heated cooling gas is conducted to the steam generators from above through a central hot gas line in the vessel. The circulating blowers are mounted horizontally on the outside of the jacket of the steel pressure vesel, requiring much space. The control and shut-down arrangements, which comprise a plurality of absorber rods that may be inserted from below into the bores of the side reflector and drives associated with them, also require much space. The side reflector may be provided with graphite projections, projecting into the pile of fuel elements. These projections would have bores into which additional absorber rods may be inserted. Small absorber spheres are provided as a diverse shut-down installation, for introduction into the fuel element pile.
Another nuclear reactor installation with a high-temperature pebble bed reactor also comprises several steam generators installed above the small reactor, in which the steam generators and the small reactor are both contained in a cylindrical steel pressure vessel. The cooling gas flows from bottom to top through both the reactor core and the steam generators. The circulating blowers are located entirely inside the steel pressure vessel, above the steam generators. This presumes a relatively large height of the steel pressure vessel. The small reactor is equipped with two diverse shut-down devices, which are again completely arranged in the steel pressure vessel. The effective elements in both shut-down installations consist of absorber spheres which may be inserted into vertical channels in the side reflector.